Where is my injection pump leaking from?

[Chuckanut]

Hey guys, I have a 1986 m1028 and I’ve had trouble starting it every day since I got it and we have replaced the lift pump and the injectors and glow plugs trying to solve the issue, but I just realized that the valley of the engine is wet, so I sprayed it down with carb cleaner and I checked every hour after the truck ran for six hours I didn’t see anything but the next morning the engine valley and a quarter way up the injection pump is wet with diesel and I’m just not sure where it’s leaking from. Any ideas?
thanks guys.

 

[WWRD99]

Hey guys, I have a 1986 m1028 and I’ve had trouble starting it every day since I got it and we have replaced the lift pump and the injectors and glow plugs trying to solve the issue, but I just realized that the valley of the engine is wet, so I sprayed it down with carb cleaner and I checked every hour after the truck ran for six hours I didn’t see anything but the next morning the engine valley and a quarter way up the injection pump is wet with diesel and I’m just not sure where it’s leaking from. Any ideas?
thanks guys.

The leak can come from the injection pump or a cracked line under there...I'd look for a thread about the lift pump as some parts catalogs will give you the wrong one...You may have replaced it with the wrong part that looks like it will work and it will not work...it's in here.

 

[Chuckanut]

The leak can come from the injection pump or a cracked line under there...I'd look for a thread about the lift pump as some parts catalogs will give you the wrong one...You may have replaced it with the wrong part that looks like it will work and it will not work...it's in here.

I know we bought the right part and it’s not the lift pump or a cracked line. The whole engine valley from the in case where it bolts to all the way to the engine valley drain at the back of the engine is wet but only the bottom of the injection pump is wet close to halfway up the sides of the pump.

 

[Keith_J]

The two most common points of leaking are the throttle shaft (both sides) and the advance mechanism (passenger side, lower). Since it runs, the core should get full rebuild value.

 

[Valor]

Hey guys, I have a 1986 m1028 and I’ve had trouble starting it every day since I got it and we have replaced the lift pump and the injectors and glow plugs trying to solve the issue, but I just realized that the valley of the engine is wet, so I sprayed it down with carb cleaner and I checked every hour after the truck ran for six hours I didn’t see anything but the next morning the engine valley and a quarter way up the injection pump is wet with diesel and I’m just not sure where it’s leaking from. Any ideas?
thanks guys.View attachment 842817View attachment 842818

Check the throttle shaft seals. They leak after time. They are small orings. I think there is only one, on driver's side. Check the TM.

 

[cucvrus]

My experience has been the throttle shaft seals are a band-aid on the real issue. The real issue is the entire injection is in need of rebuilding. I see this dance around the injection pump many times. Just do it go over the entire fuel system right up front and move on for many miles to come. Keep in mind it is a 30+ year old truck and the throttle shaft seals may have been replaced in the past. For piece of mind get the injection pump rebuilt and go over every rubber hose and clamp in the fuel system. Report back. You will pay a little bit more now but in the end you will be driving it and not working on it constantly.

 

[cucvrus]

May I also add to drop the tank and replace the fuel tank sock and sending unit it is not working accurately. Then moving forward on the fuel system replace all the hoses and clamps and replace the lift pump. Get the right size clamps. I see clamps that are for 5/8" heater hose compressed to hold 3/8" fuel hose. Really??? Do it right or just keep trying. If you didn't replace it and it looks old it needs replaced. Just get the correct lift pump the first time. Not sure why so many variations of lift pumps are listed as correct and fit and only 1 works. You want the one that has pumping action resistance immediately upon compression of the lever. ZERO free play. If it (the lever) pushes in a 1/8"-1/4" and has no resistance scrap it. You have a weak or wrong pump. Good Luck. ALWAYS here to help and I will NEVER refer you to a document to read. Schools out. I graduated from smoking in the boys room to real life experience just like many of you have. Share your true facts and if you don't know learn. Take Care.

 

[cucvrus]

Give this a try. Good Luck. Go Fund Me.

 

[cwc]

It is possible to change the advance plunger seal with the pump in place. The metal part that passes through the seal can get rusty from water sitting in the valley, so it is good to change that also especially if it is in bad shape. Another possible leak point is the drive (input) shaft seal, which will leak from a weep hole on the bottom front of the pump.

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